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<div class="title">Real FFT Functions<div class="ingroups"><a class="el" href="group__groupTransforms.html">Transform Functions</a></div></div>  </div>
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Content</h2></td></tr>
<tr class="memitem:group__RealFFT__Table"><td class="memItemLeft" align="right" valign="top">&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__RealFFT__Table.html">Real FFT Tables</a></td></tr>
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<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="func-members"></a>
Functions</h2></td></tr>
<tr class="memitem:ga3df1766d230532bc068fc4ed69d0fcdc"><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__RealFFT.html#ga3df1766d230532bc068fc4ed69d0fcdc">arm_rfft_f32</a> (const <a class="el" href="structarm__rfft__instance__f32.html">arm_rfft_instance_f32</a> *S, <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *pSrc, <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *pDst)</td></tr>
<tr class="memdesc:ga3df1766d230532bc068fc4ed69d0fcdc"><td class="mdescLeft">&#160;</td><td class="mdescRight">Processing function for the floating-point RFFT/RIFFT.  <a href="#ga3df1766d230532bc068fc4ed69d0fcdc">More...</a><br/></td></tr>
<tr class="separator:ga3df1766d230532bc068fc4ed69d0fcdc"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:ga180d8b764d59cbb85d37a2d5f7cd9799"><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__RealFFT.html#ga180d8b764d59cbb85d37a2d5f7cd9799">arm_rfft_fast_f32</a> (<a class="el" href="structarm__rfft__fast__instance__f32.html">arm_rfft_fast_instance_f32</a> *S, <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *p, <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *pOut, uint8_t <a class="el" href="arm__fft__bin__example__f32_8c.html#a379ccb99013d369a41b49619083c16ef">ifftFlag</a>)</td></tr>
<tr class="memdesc:ga180d8b764d59cbb85d37a2d5f7cd9799"><td class="mdescLeft">&#160;</td><td class="mdescRight">Processing function for the floating-point real FFT.  <a href="#ga180d8b764d59cbb85d37a2d5f7cd9799">More...</a><br/></td></tr>
<tr class="separator:ga180d8b764d59cbb85d37a2d5f7cd9799"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:ga153c8faa97b7ab8b1aef75fe6ac1b3a2"><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__RealFFT.html#ga153c8faa97b7ab8b1aef75fe6ac1b3a2">arm_rfft_32_fast_init_f32</a> (<a class="el" href="structarm__rfft__fast__instance__f32.html">arm_rfft_fast_instance_f32</a> *S)</td></tr>
<tr class="memdesc:ga153c8faa97b7ab8b1aef75fe6ac1b3a2"><td class="mdescLeft">&#160;</td><td class="mdescRight">Initialization function for the 32pt floating-point real FFT.  <a href="#ga153c8faa97b7ab8b1aef75fe6ac1b3a2">More...</a><br/></td></tr>
<tr class="separator:ga153c8faa97b7ab8b1aef75fe6ac1b3a2"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:ga0f67de6a0e5d87011f35426112d2d91b"><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__RealFFT.html#ga0f67de6a0e5d87011f35426112d2d91b">arm_rfft_64_fast_init_f32</a> (<a class="el" href="structarm__rfft__fast__instance__f32.html">arm_rfft_fast_instance_f32</a> *S)</td></tr>
<tr class="memdesc:ga0f67de6a0e5d87011f35426112d2d91b"><td class="mdescLeft">&#160;</td><td class="mdescRight">Initialization function for the 64pt floating-point real FFT.  <a href="#ga0f67de6a0e5d87011f35426112d2d91b">More...</a><br/></td></tr>
<tr class="separator:ga0f67de6a0e5d87011f35426112d2d91b"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:gade8432f9318953234761e8e0f2c9e1d2"><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__RealFFT.html#gade8432f9318953234761e8e0f2c9e1d2">arm_rfft_128_fast_init_f32</a> (<a class="el" href="structarm__rfft__fast__instance__f32.html">arm_rfft_fast_instance_f32</a> *S)</td></tr>
<tr class="memdesc:gade8432f9318953234761e8e0f2c9e1d2"><td class="mdescLeft">&#160;</td><td class="mdescRight">Initialization function for the 128pt floating-point real FFT.  <a href="#gade8432f9318953234761e8e0f2c9e1d2">More...</a><br/></td></tr>
<tr class="separator:gade8432f9318953234761e8e0f2c9e1d2"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:ga678afbb042d942c3dd5a33877ef66492"><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__RealFFT.html#ga678afbb042d942c3dd5a33877ef66492">arm_rfft_256_fast_init_f32</a> (<a class="el" href="structarm__rfft__fast__instance__f32.html">arm_rfft_fast_instance_f32</a> *S)</td></tr>
<tr class="memdesc:ga678afbb042d942c3dd5a33877ef66492"><td class="mdescLeft">&#160;</td><td class="mdescRight">Initialization function for the 256pt floating-point real FFT.  <a href="#ga678afbb042d942c3dd5a33877ef66492">More...</a><br/></td></tr>
<tr class="separator:ga678afbb042d942c3dd5a33877ef66492"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:ga9a0e72918318f9d1c03973eab379e580"><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__RealFFT.html#ga9a0e72918318f9d1c03973eab379e580">arm_rfft_512_fast_init_f32</a> (<a class="el" href="structarm__rfft__fast__instance__f32.html">arm_rfft_fast_instance_f32</a> *S)</td></tr>
<tr class="memdesc:ga9a0e72918318f9d1c03973eab379e580"><td class="mdescLeft">&#160;</td><td class="mdescRight">Initialization function for the 512pt floating-point real FFT.  <a href="#ga9a0e72918318f9d1c03973eab379e580">More...</a><br/></td></tr>
<tr class="separator:ga9a0e72918318f9d1c03973eab379e580"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:ga71547c601079d55c2525204aa00ef9c2"><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__RealFFT.html#ga71547c601079d55c2525204aa00ef9c2">arm_rfft_1024_fast_init_f32</a> (<a class="el" href="structarm__rfft__fast__instance__f32.html">arm_rfft_fast_instance_f32</a> *S)</td></tr>
<tr class="memdesc:ga71547c601079d55c2525204aa00ef9c2"><td class="mdescLeft">&#160;</td><td class="mdescRight">Initialization function for the 1024pt floating-point real FFT.  <a href="#ga71547c601079d55c2525204aa00ef9c2">More...</a><br/></td></tr>
<tr class="separator:ga71547c601079d55c2525204aa00ef9c2"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:ga33724310a8360ac289d5a835282f778c"><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__RealFFT.html#ga33724310a8360ac289d5a835282f778c">arm_rfft_2048_fast_init_f32</a> (<a class="el" href="structarm__rfft__fast__instance__f32.html">arm_rfft_fast_instance_f32</a> *S)</td></tr>
<tr class="memdesc:ga33724310a8360ac289d5a835282f778c"><td class="mdescLeft">&#160;</td><td class="mdescRight">Initialization function for the 2048pt floating-point real FFT.  <a href="#ga33724310a8360ac289d5a835282f778c">More...</a><br/></td></tr>
<tr class="separator:ga33724310a8360ac289d5a835282f778c"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:gaad50a08bb8191e1a138b5f72a268727a"><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__RealFFT.html#gaad50a08bb8191e1a138b5f72a268727a">arm_rfft_4096_fast_init_f32</a> (<a class="el" href="structarm__rfft__fast__instance__f32.html">arm_rfft_fast_instance_f32</a> *S)</td></tr>
<tr class="memdesc:gaad50a08bb8191e1a138b5f72a268727a"><td class="mdescLeft">&#160;</td><td class="mdescRight">Initialization function for the 4096pt floating-point real FFT.  <a href="#gaad50a08bb8191e1a138b5f72a268727a">More...</a><br/></td></tr>
<tr class="separator:gaad50a08bb8191e1a138b5f72a268727a"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:gac5fceb172551e7c11eb4d0e17ef15aa3"><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__RealFFT.html#gac5fceb172551e7c11eb4d0e17ef15aa3">arm_rfft_fast_init_f32</a> (<a class="el" href="structarm__rfft__fast__instance__f32.html">arm_rfft_fast_instance_f32</a> *S, uint16_t fftLen)</td></tr>
<tr class="memdesc:gac5fceb172551e7c11eb4d0e17ef15aa3"><td class="mdescLeft">&#160;</td><td class="mdescRight">Initialization function for the floating-point real FFT.  <a href="#gac5fceb172551e7c11eb4d0e17ef15aa3">More...</a><br/></td></tr>
<tr class="separator:gac5fceb172551e7c11eb4d0e17ef15aa3"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:ga10717ee326bf50832ef1c25b85a23068"><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__RealFFT.html#ga10717ee326bf50832ef1c25b85a23068">arm_rfft_init_f32</a> (<a class="el" href="structarm__rfft__instance__f32.html">arm_rfft_instance_f32</a> *S, <a class="el" href="structarm__cfft__radix4__instance__f32.html">arm_cfft_radix4_instance_f32</a> *S_CFFT, uint32_t fftLenReal, uint32_t ifftFlagR, uint32_t bitReverseFlag)</td></tr>
<tr class="memdesc:ga10717ee326bf50832ef1c25b85a23068"><td class="mdescLeft">&#160;</td><td class="mdescRight">Initialization function for the floating-point RFFT/RIFFT.  <a href="#ga10717ee326bf50832ef1c25b85a23068">More...</a><br/></td></tr>
<tr class="separator:ga10717ee326bf50832ef1c25b85a23068"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:ga053450cc600a55410ba5b5605e96245d"><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__RealFFT.html#ga053450cc600a55410ba5b5605e96245d">arm_rfft_init_q15</a> (<a class="el" href="structarm__rfft__instance__q15.html">arm_rfft_instance_q15</a> *S, uint32_t fftLenReal, uint32_t ifftFlagR, uint32_t bitReverseFlag)</td></tr>
<tr class="memdesc:ga053450cc600a55410ba5b5605e96245d"><td class="mdescLeft">&#160;</td><td class="mdescRight">Initialization function for the Q15 RFFT/RIFFT.  <a href="#ga053450cc600a55410ba5b5605e96245d">More...</a><br/></td></tr>
<tr class="separator:ga053450cc600a55410ba5b5605e96245d"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:ga5abde938abbe72e95c5bab080eb33c45"><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__RealFFT.html#ga5abde938abbe72e95c5bab080eb33c45">arm_rfft_init_q31</a> (<a class="el" href="structarm__rfft__instance__q31.html">arm_rfft_instance_q31</a> *S, uint32_t fftLenReal, uint32_t ifftFlagR, uint32_t bitReverseFlag)</td></tr>
<tr class="memdesc:ga5abde938abbe72e95c5bab080eb33c45"><td class="mdescLeft">&#160;</td><td class="mdescRight">Initialization function for the Q31 RFFT/RIFFT.  <a href="#ga5abde938abbe72e95c5bab080eb33c45">More...</a><br/></td></tr>
<tr class="separator:ga5abde938abbe72e95c5bab080eb33c45"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:ga00e615f5db21736ad5b27fb6146f3fc5"><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__RealFFT.html#ga00e615f5db21736ad5b27fb6146f3fc5">arm_rfft_q15</a> (const <a class="el" href="structarm__rfft__instance__q15.html">arm_rfft_instance_q15</a> *S, <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> *pSrc, <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> *pDst)</td></tr>
<tr class="memdesc:ga00e615f5db21736ad5b27fb6146f3fc5"><td class="mdescLeft">&#160;</td><td class="mdescRight">Processing function for the Q15 RFFT/RIFFT.  <a href="#ga00e615f5db21736ad5b27fb6146f3fc5">More...</a><br/></td></tr>
<tr class="separator:ga00e615f5db21736ad5b27fb6146f3fc5"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:gabaeab5646aeea9844e6d42ca8c73fe3a"><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group__RealFFT.html#gabaeab5646aeea9844e6d42ca8c73fe3a">arm_rfft_q31</a> (const <a class="el" href="structarm__rfft__instance__q31.html">arm_rfft_instance_q31</a> *S, <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> *pSrc, <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> *pDst)</td></tr>
<tr class="memdesc:gabaeab5646aeea9844e6d42ca8c73fe3a"><td class="mdescLeft">&#160;</td><td class="mdescRight">Processing function for the Q31 RFFT/RIFFT.  <a href="#gabaeab5646aeea9844e6d42ca8c73fe3a">More...</a><br/></td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Description</h2>
<dl class="section user"><dt></dt><dd>The CMSIS DSP library includes specialized algorithms for computing the FFT of real data sequences. The FFT is defined over complex data but in many applications the input is real. Real FFT algorithms take advantage of the symmetry properties of the FFT and have a speed advantage over complex algorithms of the same length. </dd></dl>
<dl class="section user"><dt></dt><dd>The Fast RFFT algorith relays on the mixed radix CFFT that save processor usage. </dd></dl>
<dl class="section user"><dt></dt><dd>The real length N forward FFT of a sequence is computed using the steps shown below. </dd></dl>
<dl class="section user"><dt></dt><dd><div class="image">
<img src="RFFT.gif" alt="RFFT.gif"/>
<div class="caption">
Real Fast Fourier Transform</div></div>
</dd></dl>
<dl class="section user"><dt></dt><dd>The real sequence is initially treated as if it were complex to perform a CFFT. Later, a processing stage reshapes the data to obtain half of the frequency spectrum in complex format. Except the first complex number that contains the two real numbers X[0] and X[N/2] all the data is complex. In other words, the first complex sample contains two real values packed. </dd></dl>
<dl class="section user"><dt></dt><dd>The input for the inverse RFFT should keep the same format as the output of the forward RFFT. A first processing stage pre-process the data to later perform an inverse CFFT. </dd></dl>
<dl class="section user"><dt></dt><dd><div class="image">
<img src="RIFFT.gif" alt="RIFFT.gif"/>
<div class="caption">
Real Inverse Fast Fourier Transform</div></div>
</dd></dl>
<dl class="section user"><dt></dt><dd>The algorithms for floating-point, Q15, and Q31 data are slightly different and we describe each algorithm in turn. </dd></dl>
<dl class="section user"><dt>Floating-point</dt><dd>The main functions are <a class="el" href="group__RealFFT.html#ga180d8b764d59cbb85d37a2d5f7cd9799">arm_rfft_fast_f32()</a> and <a class="el" href="group__RealFFT.html#gac5fceb172551e7c11eb4d0e17ef15aa3">arm_rfft_fast_init_f32()</a>. The older functions <a class="el" href="group__RealFFT.html#ga3df1766d230532bc068fc4ed69d0fcdc">arm_rfft_f32()</a> and <a class="el" href="group__RealFFT.html#ga10717ee326bf50832ef1c25b85a23068">arm_rfft_init_f32()</a> have been deprecated but are still documented. </dd></dl>
<dl class="section user"><dt></dt><dd>The FFT of a real N-point sequence has even symmetry in the frequency domain. The second half of the data equals the conjugate of the first half flipped in frequency. Looking at the data, we see that we can uniquely represent the FFT using only N/2 complex numbers. These are packed into the output array in alternating real and imaginary components: </dd></dl>
<dl class="section user"><dt></dt><dd>X = { real[0], imag[0], real[1], imag[1], real[2], imag[2] ... real[(N/2)-1], imag[(N/2)-1 } </dd></dl>
<dl class="section user"><dt></dt><dd>It happens that the first complex number (real[0], imag[0]) is actually all real. real[0] represents the DC offset, and imag[0] should be 0. (real[1], imag[1]) is the fundamental frequency, (real[2], imag[2]) is the first harmonic and so on. </dd></dl>
<dl class="section user"><dt></dt><dd>The real FFT functions pack the frequency domain data in this fashion. The forward transform outputs the data in this form and the inverse transform expects input data in this form. The function always performs the needed bitreversal so that the input and output data is always in normal order. The functions support lengths of [32, 64, 128, ..., 4096] samples. </dd></dl>
<dl class="section user"><dt>Q15 and Q31</dt><dd>The real algorithms are defined in a similar manner and utilize N/2 complex transforms behind the scenes. </dd></dl>
<dl class="section user"><dt></dt><dd>The complex transforms used internally include scaling to prevent fixed-point overflows. The overall scaling equals 1/(fftLen/2). </dd></dl>
<dl class="section user"><dt></dt><dd>A separate instance structure must be defined for each transform used but twiddle factor and bit reversal tables can be reused. </dd></dl>
<dl class="section user"><dt></dt><dd>There is also an associated initialization function for each data type. The initialization function performs the following operations:<ul>
<li>Sets the values of the internal structure fields.</li>
<li>Initializes twiddle factor table and bit reversal table pointers.</li>
<li>Initializes the internal complex FFT data structure. </li>
</ul>
</dd></dl>
<dl class="section user"><dt></dt><dd>Use of the initialization function is optional. However, if the initialization function is used, then the instance structure cannot be placed into a const data section. To place an instance structure into a const data section, the instance structure should be manually initialized as follows: <pre>
    <a class="el" href="structarm__rfft__instance__q31.html" title="Instance structure for the Q31 RFFT/RIFFT function. ">arm_rfft_instance_q31</a> S = {fftLenReal, fftLenBy2, ifftFlagR, bitReverseFlagR, twidCoefRModifier, pTwiddleAReal, pTwiddleBReal, pCfft};
    <a class="el" href="structarm__rfft__instance__q15.html" title="Instance structure for the Q15 RFFT/RIFFT function. ">arm_rfft_instance_q15</a> S = {fftLenReal, fftLenBy2, ifftFlagR, bitReverseFlagR, twidCoefRModifier, pTwiddleAReal, pTwiddleBReal, pCfft};
</pre> where <code>fftLenReal</code> is the length of the real transform; <code>fftLenBy2</code> length of the internal complex transform. <code>ifftFlagR</code> Selects forward (=0) or inverse (=1) transform. <code>bitReverseFlagR</code> Selects bit reversed output (=0) or normal order output (=1). <code>twidCoefRModifier</code> stride modifier for the twiddle factor table. The value is based on the FFT length; <code>pTwiddleAReal</code>points to the A array of twiddle coefficients; <code>pTwiddleBReal</code>points to the B array of twiddle coefficients; <code>pCfft</code> points to the CFFT Instance structure. The CFFT structure must also be initialized. Refer to <a class="el" href="group__ComplexFFT.html#ga521f670cd9c571bc61aff9bec89f4c26" title="Processing function for the floating-point Radix-4 CFFT/CIFFT. ">arm_cfft_radix4_f32()</a> for details regarding static initialization of the complex FFT instance structure. </dd></dl>
<h2 class="groupheader">Function Documentation</h2>
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          <td class="memname"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a> arm_rfft_1024_fast_init_f32 </td>
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          <td class="paramname"><em>S</em></td><td>)</td>
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<dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramdir">[in,out]</td><td class="paramname">S</td><td>points to an <a class="el" href="structarm__rfft__fast__instance__f32.html" title="Instance structure for the floating-point RFFT/RIFFT function. ">arm_rfft_fast_instance_f32</a> structure </td></tr>
  </table>
  </dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>execution status<ul>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a9f8b2a10bd827fb4600e77d455902eb0">ARM_MATH_SUCCESS</a> : Operation successful</li>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a74897e18d4b8f62b12a7d8a01dd2bb35">ARM_MATH_ARGUMENT_ERROR</a> : an error is detected </li>
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          <td class="memname"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a> arm_rfft_128_fast_init_f32 </td>
          <td>(</td>
          <td class="paramtype"><a class="el" href="structarm__rfft__fast__instance__f32.html">arm_rfft_fast_instance_f32</a> *&#160;</td>
          <td class="paramname"><em>S</em></td><td>)</td>
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<dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramdir">[in,out]</td><td class="paramname">S</td><td>points to an <a class="el" href="structarm__rfft__fast__instance__f32.html" title="Instance structure for the floating-point RFFT/RIFFT function. ">arm_rfft_fast_instance_f32</a> structure </td></tr>
  </table>
  </dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>execution status<ul>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a9f8b2a10bd827fb4600e77d455902eb0">ARM_MATH_SUCCESS</a> : Operation successful</li>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a74897e18d4b8f62b12a7d8a01dd2bb35">ARM_MATH_ARGUMENT_ERROR</a> : an error is detected </li>
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          <td>(</td>
          <td class="paramtype"><a class="el" href="structarm__rfft__fast__instance__f32.html">arm_rfft_fast_instance_f32</a> *&#160;</td>
          <td class="paramname"><em>S</em></td><td>)</td>
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<dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramdir">[in,out]</td><td class="paramname">S</td><td>points to an <a class="el" href="structarm__rfft__fast__instance__f32.html" title="Instance structure for the floating-point RFFT/RIFFT function. ">arm_rfft_fast_instance_f32</a> structure </td></tr>
  </table>
  </dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>execution status<ul>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a9f8b2a10bd827fb4600e77d455902eb0">ARM_MATH_SUCCESS</a> : Operation successful</li>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a74897e18d4b8f62b12a7d8a01dd2bb35">ARM_MATH_ARGUMENT_ERROR</a> : an error is detected </li>
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          <td>(</td>
          <td class="paramtype"><a class="el" href="structarm__rfft__fast__instance__f32.html">arm_rfft_fast_instance_f32</a> *&#160;</td>
          <td class="paramname"><em>S</em></td><td>)</td>
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<dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramdir">[in,out]</td><td class="paramname">S</td><td>points to an <a class="el" href="structarm__rfft__fast__instance__f32.html" title="Instance structure for the floating-point RFFT/RIFFT function. ">arm_rfft_fast_instance_f32</a> structure </td></tr>
  </table>
  </dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>execution status<ul>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a9f8b2a10bd827fb4600e77d455902eb0">ARM_MATH_SUCCESS</a> : Operation successful</li>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a74897e18d4b8f62b12a7d8a01dd2bb35">ARM_MATH_ARGUMENT_ERROR</a> : an error is detected </li>
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<dl class="params"><dt>Parameters</dt><dd>
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    <tr><td class="paramdir">[in,out]</td><td class="paramname">S</td><td>points to an <a class="el" href="structarm__rfft__fast__instance__f32.html" title="Instance structure for the floating-point RFFT/RIFFT function. ">arm_rfft_fast_instance_f32</a> structure </td></tr>
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<dl class="section return"><dt>Returns</dt><dd>execution status<ul>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a9f8b2a10bd827fb4600e77d455902eb0">ARM_MATH_SUCCESS</a> : Operation successful</li>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a74897e18d4b8f62b12a7d8a01dd2bb35">ARM_MATH_ARGUMENT_ERROR</a> : an error is detected </li>
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          <td class="paramname"><em>S</em></td><td>)</td>
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<dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramdir">[in,out]</td><td class="paramname">S</td><td>points to an <a class="el" href="structarm__rfft__fast__instance__f32.html" title="Instance structure for the floating-point RFFT/RIFFT function. ">arm_rfft_fast_instance_f32</a> structure </td></tr>
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  </dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>execution status<ul>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a9f8b2a10bd827fb4600e77d455902eb0">ARM_MATH_SUCCESS</a> : Operation successful</li>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a74897e18d4b8f62b12a7d8a01dd2bb35">ARM_MATH_ARGUMENT_ERROR</a> : an error is detected </li>
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          <td class="paramname"><em>S</em></td><td>)</td>
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<dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramdir">[in,out]</td><td class="paramname">S</td><td>points to an <a class="el" href="structarm__rfft__fast__instance__f32.html" title="Instance structure for the floating-point RFFT/RIFFT function. ">arm_rfft_fast_instance_f32</a> structure </td></tr>
  </table>
  </dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>execution status<ul>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a9f8b2a10bd827fb4600e77d455902eb0">ARM_MATH_SUCCESS</a> : Operation successful</li>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a74897e18d4b8f62b12a7d8a01dd2bb35">ARM_MATH_ARGUMENT_ERROR</a> : an error is detected </li>
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          <td class="paramtype"><a class="el" href="structarm__rfft__fast__instance__f32.html">arm_rfft_fast_instance_f32</a> *&#160;</td>
          <td class="paramname"><em>S</em></td><td>)</td>
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<dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramdir">[in,out]</td><td class="paramname">S</td><td>points to an <a class="el" href="structarm__rfft__fast__instance__f32.html" title="Instance structure for the floating-point RFFT/RIFFT function. ">arm_rfft_fast_instance_f32</a> structure </td></tr>
  </table>
  </dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>execution status<ul>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a9f8b2a10bd827fb4600e77d455902eb0">ARM_MATH_SUCCESS</a> : Operation successful</li>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a74897e18d4b8f62b12a7d8a01dd2bb35">ARM_MATH_ARGUMENT_ERROR</a> : an error is detected </li>
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          <td class="memname">void arm_rfft_f32 </td>
          <td>(</td>
          <td class="paramtype">const <a class="el" href="structarm__rfft__instance__f32.html">arm_rfft_instance_f32</a> *&#160;</td>
          <td class="paramname"><em>S</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype"><a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *&#160;</td>
          <td class="paramname"><em>pSrc</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype"><a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *&#160;</td>
          <td class="paramname"><em>pDst</em>&#160;</td>
        </tr>
        <tr>
          <td></td>
          <td>)</td>
          <td></td><td></td>
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<dl class="deprecated"><dt><b><a class="el" href="deprecated.html#_deprecated000014">Deprecated:</a></b></dt><dd>Do not use this function. It has been superceded by <a class="el" href="group__RealFFT.html#ga180d8b764d59cbb85d37a2d5f7cd9799">arm_rfft_fast_f32</a> and will be removed in the future. <dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramdir">[in]</td><td class="paramname">S</td><td>points to an instance of the floating-point RFFT/RIFFT structure </td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">pSrc</td><td>points to the input buffer </td></tr>
    <tr><td class="paramdir">[out]</td><td class="paramname">pDst</td><td>points to the output buffer </td></tr>
  </table>
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</dl>
<dl class="section return"><dt>Returns</dt><dd>none </dd></dl>
</dd></dl>

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          <td class="memname">void arm_rfft_fast_f32 </td>
          <td>(</td>
          <td class="paramtype"><a class="el" href="structarm__rfft__fast__instance__f32.html">arm_rfft_fast_instance_f32</a> *&#160;</td>
          <td class="paramname"><em>S</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype"><a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *&#160;</td>
          <td class="paramname"><em>p</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype"><a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *&#160;</td>
          <td class="paramname"><em>pOut</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype">uint8_t&#160;</td>
          <td class="paramname"><em>ifftFlag</em>&#160;</td>
        </tr>
        <tr>
          <td></td>
          <td>)</td>
          <td></td><td></td>
        </tr>
      </table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramdir">[in]</td><td class="paramname">S</td><td>points to an <a class="el" href="structarm__rfft__fast__instance__f32.html" title="Instance structure for the floating-point RFFT/RIFFT function. ">arm_rfft_fast_instance_f32</a> structure </td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">p</td><td>points to input buffer </td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">pOut</td><td>points to output buffer </td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">ifftFlag</td><td><ul>
<li>value = 0: RFFT</li>
<li>value = 1: RIFFT </li>
</ul>
</td></tr>
  </table>
  </dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>none </dd></dl>

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          <td class="memname"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a> arm_rfft_fast_init_f32 </td>
          <td>(</td>
          <td class="paramtype"><a class="el" href="structarm__rfft__fast__instance__f32.html">arm_rfft_fast_instance_f32</a> *&#160;</td>
          <td class="paramname"><em>S</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype">uint16_t&#160;</td>
          <td class="paramname"><em>fftLen</em>&#160;</td>
        </tr>
        <tr>
          <td></td>
          <td>)</td>
          <td></td><td></td>
        </tr>
      </table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramdir">[in,out]</td><td class="paramname">S</td><td>points to an <a class="el" href="structarm__rfft__fast__instance__f32.html" title="Instance structure for the floating-point RFFT/RIFFT function. ">arm_rfft_fast_instance_f32</a> structure </td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">fftLen</td><td>length of the Real Sequence </td></tr>
  </table>
  </dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>execution status<ul>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a9f8b2a10bd827fb4600e77d455902eb0">ARM_MATH_SUCCESS</a> : Operation successful</li>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a74897e18d4b8f62b12a7d8a01dd2bb35">ARM_MATH_ARGUMENT_ERROR</a> : <code>fftLen</code> is not a supported length</li>
</ul>
</dd></dl>
<dl class="section user"><dt>Description</dt><dd>The parameter <code>fftLen</code> specifies the length of RFFT/CIFFT process. Supported FFT Lengths are 32, 64, 128, 256, 512, 1024, 2048, 4096. </dd></dl>
<dl class="section user"><dt></dt><dd>This Function also initializes Twiddle factor table pointer and Bit reversal table pointer. </dd></dl>

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          <td class="memname"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a> arm_rfft_init_f32 </td>
          <td>(</td>
          <td class="paramtype"><a class="el" href="structarm__rfft__instance__f32.html">arm_rfft_instance_f32</a> *&#160;</td>
          <td class="paramname"><em>S</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype"><a class="el" href="structarm__cfft__radix4__instance__f32.html">arm_cfft_radix4_instance_f32</a> *&#160;</td>
          <td class="paramname"><em>S_CFFT</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype">uint32_t&#160;</td>
          <td class="paramname"><em>fftLenReal</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype">uint32_t&#160;</td>
          <td class="paramname"><em>ifftFlagR</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype">uint32_t&#160;</td>
          <td class="paramname"><em>bitReverseFlag</em>&#160;</td>
        </tr>
        <tr>
          <td></td>
          <td>)</td>
          <td></td><td></td>
        </tr>
      </table>
</div><div class="memdoc">
<dl class="deprecated"><dt><b><a class="el" href="deprecated.html#_deprecated000015">Deprecated:</a></b></dt><dd>Do not use this function. It has been superceded by <a class="el" href="group__RealFFT.html#gac5fceb172551e7c11eb4d0e17ef15aa3">arm_rfft_fast_init_f32</a> and will be removed in the future. <dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramdir">[in,out]</td><td class="paramname">S</td><td>points to an instance of the floating-point RFFT/RIFFT structure </td></tr>
    <tr><td class="paramdir">[in,out]</td><td class="paramname">S_CFFT</td><td>points to an instance of the floating-point CFFT/CIFFT structure </td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">fftLenReal</td><td>length of the FFT. </td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">ifftFlagR</td><td>flag that selects transform direction<ul>
<li>value = 0: forward transform</li>
<li>value = 1: inverse transform </li>
</ul>
</td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">bitReverseFlag</td><td>flag that enables / disables bit reversal of output<ul>
<li>value = 0: disables bit reversal of output</li>
<li>value = 1: enables bit reversal of output </li>
</ul>
</td></tr>
  </table>
  </dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>execution status<ul>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a9f8b2a10bd827fb4600e77d455902eb0">ARM_MATH_SUCCESS</a> : Operation successful</li>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a74897e18d4b8f62b12a7d8a01dd2bb35">ARM_MATH_ARGUMENT_ERROR</a> : <code>fftLenReal</code> is not a supported length</li>
</ul>
</dd></dl>
</dd></dl>
<dl class="section user"><dt>Description</dt><dd>The parameter <code>fftLenReal</code>specifies length of RFFT/RIFFT Process. Supported FFT Lengths are 128, 512, 2048. </dd></dl>
<dl class="section user"><dt></dt><dd>The parameter <code>ifftFlagR</code> controls whether a forward or inverse transform is computed. Set(=1) ifftFlagR to calculate RIFFT, otherwise RFFT is calculated. </dd></dl>
<dl class="section user"><dt></dt><dd>The parameter <code>bitReverseFlag</code> controls whether output is in normal order or bit reversed order. Set(=1) bitReverseFlag for output to be in normal order otherwise output is in bit reversed order. </dd></dl>
<dl class="section user"><dt></dt><dd>This function also initializes Twiddle factor table. </dd></dl>

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          <td class="memname"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a> arm_rfft_init_q15 </td>
          <td>(</td>
          <td class="paramtype"><a class="el" href="structarm__rfft__instance__q15.html">arm_rfft_instance_q15</a> *&#160;</td>
          <td class="paramname"><em>S</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype">uint32_t&#160;</td>
          <td class="paramname"><em>fftLenReal</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype">uint32_t&#160;</td>
          <td class="paramname"><em>ifftFlagR</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype">uint32_t&#160;</td>
          <td class="paramname"><em>bitReverseFlag</em>&#160;</td>
        </tr>
        <tr>
          <td></td>
          <td>)</td>
          <td></td><td></td>
        </tr>
      </table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramdir">[in,out]</td><td class="paramname">S</td><td>points to an instance of the Q15 RFFT/RIFFT structure </td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">fftLenReal</td><td>length of the FFT </td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">ifftFlagR</td><td>flag that selects transform direction<ul>
<li>value = 0: forward transform</li>
<li>value = 1: inverse transform </li>
</ul>
</td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">bitReverseFlag</td><td>flag that enables / disables bit reversal of output<ul>
<li>value = 0: disables bit reversal of output</li>
<li>value = 1: enables bit reversal of output </li>
</ul>
</td></tr>
  </table>
  </dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>execution status<ul>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a9f8b2a10bd827fb4600e77d455902eb0">ARM_MATH_SUCCESS</a> : Operation successful</li>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a74897e18d4b8f62b12a7d8a01dd2bb35">ARM_MATH_ARGUMENT_ERROR</a> : <code>fftLenReal</code> is not a supported length</li>
</ul>
</dd></dl>
<dl class="section user"><dt>Details</dt><dd>The parameter <code>fftLenReal</code> specifies length of RFFT/RIFFT Process. Supported FFT Lengths are 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192. </dd></dl>
<dl class="section user"><dt></dt><dd>The parameter <code>ifftFlagR</code> controls whether a forward or inverse transform is computed. Set(=1) ifftFlagR to calculate RIFFT, otherwise RFFT is calculated. </dd></dl>
<dl class="section user"><dt></dt><dd>The parameter <code>bitReverseFlag</code> controls whether output is in normal order or bit reversed order. Set(=1) bitReverseFlag for output to be in normal order otherwise output is in bit reversed order. </dd></dl>
<dl class="section user"><dt></dt><dd>This function also initializes Twiddle factor table. </dd></dl>

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          <td class="memname"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a> arm_rfft_init_q31 </td>
          <td>(</td>
          <td class="paramtype"><a class="el" href="structarm__rfft__instance__q31.html">arm_rfft_instance_q31</a> *&#160;</td>
          <td class="paramname"><em>S</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype">uint32_t&#160;</td>
          <td class="paramname"><em>fftLenReal</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype">uint32_t&#160;</td>
          <td class="paramname"><em>ifftFlagR</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype">uint32_t&#160;</td>
          <td class="paramname"><em>bitReverseFlag</em>&#160;</td>
        </tr>
        <tr>
          <td></td>
          <td>)</td>
          <td></td><td></td>
        </tr>
      </table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramdir">[in,out]</td><td class="paramname">S</td><td>points to an instance of the Q31 RFFT/RIFFT structure </td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">fftLenReal</td><td>length of the FFT </td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">ifftFlagR</td><td>flag that selects transform direction<ul>
<li>value = 0: forward transform</li>
<li>value = 1: inverse transform </li>
</ul>
</td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">bitReverseFlag</td><td>flag that enables / disables bit reversal of output<ul>
<li>value = 0: disables bit reversal of output</li>
<li>value = 1: enables bit reversal of output </li>
</ul>
</td></tr>
  </table>
  </dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>execution status<ul>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a9f8b2a10bd827fb4600e77d455902eb0">ARM_MATH_SUCCESS</a> : Operation successful</li>
<li><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6a74897e18d4b8f62b12a7d8a01dd2bb35">ARM_MATH_ARGUMENT_ERROR</a> : <code>fftLenReal</code> is not a supported length</li>
</ul>
</dd></dl>
<dl class="section user"><dt>Details</dt><dd>The parameter <code>fftLenReal</code> specifies length of RFFT/RIFFT Process. Supported FFT Lengths are 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192. </dd></dl>
<dl class="section user"><dt></dt><dd>The parameter <code>ifftFlagR</code> controls whether a forward or inverse transform is computed. Set(=1) ifftFlagR to calculate RIFFT, otherwise RFFT is calculated. </dd></dl>
<dl class="section user"><dt></dt><dd>The parameter <code>bitReverseFlag</code> controls whether output is in normal order or bit reversed order. Set(=1) bitReverseFlag for output to be in normal order otherwise output is in bit reversed order. </dd></dl>
<dl class="section user"><dt></dt><dd>This function also initializes Twiddle factor table. </dd></dl>

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          <td class="memname">void arm_rfft_q15 </td>
          <td>(</td>
          <td class="paramtype">const <a class="el" href="structarm__rfft__instance__q15.html">arm_rfft_instance_q15</a> *&#160;</td>
          <td class="paramname"><em>S</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype"><a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> *&#160;</td>
          <td class="paramname"><em>pSrc</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype"><a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> *&#160;</td>
          <td class="paramname"><em>pDst</em>&#160;</td>
        </tr>
        <tr>
          <td></td>
          <td>)</td>
          <td></td><td></td>
        </tr>
      </table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramdir">[in]</td><td class="paramname">S</td><td>points to an instance of the Q15 RFFT/RIFFT structure </td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">pSrc</td><td>points to input buffer </td></tr>
    <tr><td class="paramdir">[out]</td><td class="paramname">pDst</td><td>points to output buffer </td></tr>
  </table>
  </dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>none</dd></dl>
<dl class="section user"><dt>Input an output formats</dt><dd>Internally input is downscaled by 2 for every stage to avoid saturations inside CFFT/CIFFT process. Hence the output format is different for different RFFT sizes. The input and output formats for different RFFT sizes and number of bits to upscale are mentioned in the tables below for RFFT and RIFFT: </dd></dl>
<dl class="section user"><dt></dt><dd><div class="image">
<img src="RFFTQ15.gif" alt="RFFTQ15.gif"/>
<div class="caption">
Input and Output Formats for Q15 RFFT</div></div>
</dd></dl>
<dl class="section user"><dt></dt><dd><div class="image">
<img src="RIFFTQ15.gif" alt="RIFFTQ15.gif"/>
<div class="caption">
Input and Output Formats for Q15 RIFFT</div></div>
</dd></dl>

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          <td class="memname">void arm_rfft_q31 </td>
          <td>(</td>
          <td class="paramtype">const <a class="el" href="structarm__rfft__instance__q31.html">arm_rfft_instance_q31</a> *&#160;</td>
          <td class="paramname"><em>S</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> *&#160;</td>
          <td class="paramname"><em>pSrc</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> *&#160;</td>
          <td class="paramname"><em>pDst</em>&#160;</td>
        </tr>
        <tr>
          <td></td>
          <td>)</td>
          <td></td><td></td>
        </tr>
      </table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramdir">[in]</td><td class="paramname">S</td><td>points to an instance of the Q31 RFFT/RIFFT structure </td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">pSrc</td><td>points to input buffer </td></tr>
    <tr><td class="paramdir">[out]</td><td class="paramname">pDst</td><td>points to output buffer </td></tr>
  </table>
  </dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>none</dd></dl>
<dl class="section user"><dt>Input an output formats</dt><dd>Internally input is downscaled by 2 for every stage to avoid saturations inside CFFT/CIFFT process. Hence the output format is different for different RFFT sizes. The input and output formats for different RFFT sizes and number of bits to upscale are mentioned in the tables below for RFFT and RIFFT: </dd></dl>
<dl class="section user"><dt></dt><dd><div class="image">
<img src="RFFTQ31.gif" alt="RFFTQ31.gif"/>
<div class="caption">
Input and Output Formats for Q31 RFFT</div></div>
</dd></dl>
<dl class="section user"><dt></dt><dd><div class="image">
<img src="RIFFTQ31.gif" alt="RIFFTQ31.gif"/>
<div class="caption">
Input and Output Formats for Q31 RIFFT</div></div>
</dd></dl>

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